Iowa is likely to see more: The state has gotten warmer over the past 30 years, and scientists expect the years ahead will get even hotter, a shift that's likely to hit cities with more frequent and intense rainstorms, similar to the torrential rains that ravaged parts of the Des Moines metro in late June.

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John Swanson, a watershed management authority coordinator for Polk Soil and Water, stands in an oxbow restoration area at Waterford Park on 156th Street in Urbandale on Tuesday, July. 31, 2018.
Bryon Houlgrave/The Register

Updates have been made recently at a culvert on 30th and Jefferson, north of Drake University in Des Moines. The culvert is capable now of handling large amounts of water in the event of heavy rainfall.
Bryon Houlgrave/The Register

Vegetation and trees native to the Iowa prairies will remain intact as an oxbow is built at Waterford Park in Urbandale. The park, once complete, will also feature a playground and a bicycle trail.
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Vegetation and trees native to the Iowa prairies will remain intact as an oxbow is built at Waterford Park in Urbandale. The park, once complete, will also feature a playground and a bicycle trail.
Bryon Houlgrave/The Register

Vegetation and trees native to the Iowa prairies will remain intact as an oxbow is built at Waterford Park in Urbandale. The park, once complete, will also feature a playground and a bicycle trail.
Bryon Houlgrave/The Register

Updates have been made recently at a culvert on 30th and Jefferson, north of Drake University in Des Moines. The culvert is capable now of handling large amounts of water in the event of heavy rainfall.
Bryon Houlgrave/The Register

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"We are experiencing what the rest of the planet is experiencing. ... Wet areas are getting wetter, and dry areas are getting drier," said Jerry Schnoor, a University of Iowa professor in civil and environmental engineering.

Iowa is 1.3 degrees Fahrenheit warmer since 1988, according to an Associated Press analysis of weather data. Northwest Iowa has seen the greatest increase in temperature at 1.67 degrees, and the southeast has seen the smallest at 0.8 degrees, the data show.

Every other state warmed, too. The national annual average temperature climbed 1.6 degrees from 1988 to 2017. Alaska, Vermont and New Jersey posted the largest gains, and Washington, Oregon and North Dakota, the smallest.

Iowa ranked 38th among U.S. states.

Warming over the Gulf of Mexico is helping feed large rain events in Iowa and the Midwest, Schnoor said: "That's why we're prone to these great downpours like Des Moines saw on June 30."

Climate change, combined with rapid development and increased drainage from upstream farmland, have city, state and federal leaders scrambling to make adjustments.

They're installing bigger pipes to carry larger amounts of stormwater; reassessing how they build roads, bridges and levees; restoring oxbows and wetlands within cities; and increasing the release of water from reservoirs like Saylorville Lake, designed to prevent flooding.

Cities are even looking for flooding mitigation answers outside their metropolitan boundaries.

Clive, for example, is asking federal agencies to assess whether development over three decades would justify building upstream flood-control lakes, reservoirs or wetlands.

Officials estimate the Des Moines metro could see up to 12,000 more acres of development in the Walnut Creek watershed. It could add roughly $12 billion in value, with development stretching west to Dallas Center and north to Grimes.

"The sheer volume of new development would create, I would expect, a measurable downstream impact," said Doug Ollendike, Clive's community development director.

The city wants to know "how much worse the damage could get from increased flooding" in Walnut Creek.

Rising temperatures mean more intense rains

"It’s not a large increase in temperature, in the sense of people noticing or feeling it," said Schnoor, co-director of the UI's Center for Global and Regional Environmental Research.

But it's significant because "it reflects a warming of the planet and warming of the oceans," he said.

Importantly for Iowa, the Gulf of Mexico is warming, generating more moisture that can be pulled into the states.

That has meant more frequent and intense rain events.

For example, six of the eight wettest years on record in Iowa have occurred since 1982.

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Raydar Milton, a technician with the Osage Municipal Utilities, observes the damage to a portion of Highway 9 west of Osage on May 20, 2013 after a flash flood washed part of a culvert away during a band of intense storms the previous day.(Photo: Bryon Houlgrave/The Register)

The flash flood that hit Des Moines, Schnoor said, "might have occurred once in 500 years, prior to climate change ... but now, it's much more common."

Iowa's temperatures — and rain events — will likely ramp up, said Schnoor and Gene Takle, an Iowa State University emeritus agronomy professor.

Five out of every 10 years, a five-day heat wave now averages 90 to 95 degrees in central Iowa, Takle said. By 2050, the average will climb 7 degrees.

And once every 10 years, it will spike 13 degrees, pushing the five-day heat wave as high as 108 degrees Fahrenheit, said Takle, who is contributing to the Fourth National Climate Assessment, a scientific analysis of climate change, mandated by the 1990 Global Change Research Act.

"The projections for the future are quite sobering," he said, adding that the impact will affect businesses, people and governments.

Farming, historically important in Iowa and making up about a quarter of the state economy, could be among the industries hardest hit.

Imagine corn trying to pollinate in a 108-degree oven, Takle said.

"It's a no-brainer. Pollination can’t occur at those temperatures," he said.

"And if you raise the temperature in those hog buildings by 13 degrees Fahrenheit in the dead of summer, no amount of additional air movement by fans is going to cool" them.

"They'll have to look at adding air-conditioning," Takle said.

A call for cities, farmers to work together

In a forgotten wetland in Urbandale, John Swanson points to a restored oxbow that will help hold and slow water that runs off a nearby residential development under construction.

"Roads and rooftops don't hold water," said Swanson, a watershed management coordinator for the Polk Soil and Water Conservation District.

The oxbow, snaking through the valley, worked to slow June's rains from rushing downstream.

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Vegetation and trees native to the Iowa prairies will remain intact as an oxbow is built at Waterford Park in Urbandale. The park, once complete, will also feature a playground and a bicycle trail.(Photo: Bryon Houlgrave/The Register)

"We want to hold the water back, before it gains momentum," Swanson said. Otherwise, "by the time the water gets to Clive, there's nothing they can do. There's simply too much."

That's why central Iowa leaders are trying to work together, reaching out to farmers upstream, to fight flooding, Swanson said.

Teaming up can help upstream growers add conservation practices that improve or protect soil, or help pay to take environmentally sensitive land out of production.

"It's what makes this complicated: Clive can't do it by itself. Urbandale can't do it by itself. And farmers can't do it by themselves. No one alone has enough money to do it all by themselves," Swanson said.

He and his co-workers are talking with developers, farmers and other landowners about places where more wetlands, ponds and other flood-control measures could be built to help "keep water where it falls."

The practices also can improve water quality by cutting nitrogen, phosphorus and bacteria levels that threaten drinking water supplies.

The storage needs are great: The Fourmile Creek watershed management plan calls for building about ​​​​​​​600 acre-feetof upstream storage, for example. An acre-foot is the volume of water necessary to cover 1 acre of surface area to a depth of 1 foot.

After two large retention projects fell apart, Swanson hopes the area's first 200 acre-feet project will come together in Ankeny.

"It's a long process, putting together willing landowners," Swanson said.

It's not just large floods that drive the need: With development, storms with less than 3 inches of rain now have a greater impact than those with close to 5 inches when the state was covered with prairie.

Streams deepen and widen with more water running through them, Swanson said.

"That's bad for the environment," he said.

"But it will impact residents, too, when houses start falling into the water. And when their cities have to spend millions stabilizing streams."

A truck drives through flood waters at the intersection of Sixth Avenue and Holcomb Avenue outside of North High School after rain storms caused flooding through out the metro on Saturday, June 30, 2018.
Kelsey Kremer/The Register

Two men sit stranded in their cars, surrounded by flood water from Fourmile Creek on the bridge at the intersection of Hubbell Avenue and East 33rd Street on Des Moines' east side on Sunday morning, July 1, 2018 after heavy rain fell overnight. The creek crested at a record 17.47 feet around 6:00 A.M..
Kelsey Kremer/The Register

Des Moines fire and rescue crews assist two men sit stranded in their cars, surrounded by flood water from Fourmile Creek on the bridge at the intersection of Hubbell Avenue and East 33rd Street on Des Moines' east side on Sunday morning, July 1, 2018 after heavy rain fell overnight. The creek crested at a record 17.47 feet around 6:00 A.M..
Kelsey Kremer/The Register

Des Moines fire and rescue crews assist two men sit stranded in their cars, surrounded by flood water from Fourmile Creek on the bridge at the intersection of Hubbell Avenue and East 33rd Street on Des Moines' east side on Sunday morning, July 1, 2018 after heavy rain fell overnight. The creek crested at a record 17.47 feet around 6:00 A.M..
Kelsey Kremer/The Register

Iowa Governor Kim Reynolds embraces Beverly Phillips, of Des Moines, outside her home while touring flood damaged areas of Polk County on Monday, July 2, 2018, on Des Moines's east side. Phillips' home was flooded by Fourmile Creek on Saturday.
Kelsey Kremer/The Register

Shane Rhoades returns to his home that exploded during the flash flood last night on Sunday, July 1, 2018, in Urbandale. Rhoades said he and his wife were overtaken by water while in their basement but were saved when a wall gave out and they were swept outside.
Brian Powers/The Register

Iowa Gov. Kim Reynolds visits Beverly Phillips, of Des Moines, outside her home while touring flood damaged areas of Polk County on Monday, July 2, 2018, on Des Moines's east side. Phillips' home was flooded by Fourmile Creek on Saturday.
Kelsey Kremer/The Register

Water inundates the intersection of 56th Street and New York Avenue after a flash flooding event on Saturday, June 30, 2018, in Des Moines. Several cars were stuck in the flood water.
Kelsey Kremer/The Register

A group of people stranded by flood water watch as it slowly recedes from the intersection of Sixth Avenue and Holcomb Avenue outside of North High School after rain storms caused flooding through out the metro on Saturday, June 30, 2018.
Kelsey Kremer/The Register

Steve Lucas of Waukee, right, helps sort through the wood he, brother Eric Bauer, left, and Bauer's son Austin, 7, center, tore out of their parents basement on Sunday, July 1, 2018, in Clive. They said there was about eight inches of water in the basement and everything needed to go.
Brian Powers/The Register

Steve Lucas of Waukee, right, helps sort through the wood he, brother Eric Bauer, left, and Bauer's son Austin, 7, center, tore out of their parents basement on Sunday, July 1, 2018, in Clive. They said there was about eight inches of water in the basement and everything needed to go.
Brian Powers/The Register

A car sits abandoned in flood water from Fourmile Creek near the intersection of Hubbell Avenue and East 33rd Street on Des Moines' east side on Sunday morning, July 1, 2018 after heavy rain fell overnight. The creek crested at a record 17.47 feet around 6:00 A.M..
Kelsey Kremer/The Register

Shane Rhoades returns to his home that exploded during the flash flood last night on Sunday, July 1, 2018, in Urbandale. Rhoades said he and his wife were overtaken by water while in their basement but were saved when a wall gave out and they were swept outside.
Brian Powers/The Register

Shane Rhoades returns to his home that exploded during the flash flood last night on Sunday, July 1, 2018, in Urbandale. Rhoades said he and his wife were overtaken by water while in their basement but were saved when a wall gave out and they were swept outside.
Brian Powers/The Register

Friends of Christine Zoller balance a canoe while carrying her television from her North Hampshire Avenue home after flood waters receded and residents began to assess damages June 9, 2008, in Mason City.
Register File Photo

David Mejia, 12, of Mason City takes a break while helping Christine Zoller move belongings from her North Hampshire Avenue home via canoe as flood waters receded and residents began to assess damages June 9, 2008, in Mason City.
Register File Photo

Rick Primmer, owner of a trucking company of Vinton, waits as his semi-truck is loaded with furniture and records from the Benton County Sheriff's office in the flooded city of Vinton on June 11, 2008, which he planned to transport to dry storage facilities. The truck had to be towed out of the high water. Vinton is one of several major cities in the state of Iowa that are flooded due to rising rivers from multiple storms.
Register File Photo

Flood waters surround train cars (top) and semi-trailers in Cedar Rapids, Iowa, June 12, 2008. Heavy rains pounded large portions of Iowa, with rivers cresting at record levels in many parts of the state.
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Spc. Robert Curtis, of Cedar Rapids, wades through flood water with other Iowa Army National Guard soldiers in the city of Vinton on June 11, 2008. The soldiers arrived on Tuesday night to help with flood relief efforts. Vinton is one of multiple cities flooding in the state of Iowa.
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Spc. Curtis White (left center) and Daniele Ritter are married June 19, 2008, by Chaplin Captain Murray Phillips (center, back to camera) on the viaduct over downtown Columbus Junction as cleanup work continues from flooding from the Iowa River.
Rodney White/The Register

Ryan Davis 13 of Des Moines tries to make it across Saylor Road in the flood waters in Union Park Wednesday afternoon. He wisely turned around. With the flood gates lowered at the Salorville Dam water is on the rise in Des Moines June 11, 2008.
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Brian Flaherty, right, unloads tools from a boat at the intersection of NW Beaver Drive and Johnston Drive June 13, 2008 in Johnston. Flaherty works for Turfwerks, one of the flooded businesses in the area. Flood water about four feet deep covers NW Beaver Drive.
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Bradley Cleveland takes a photo of and Peter LeVake after he waded out to a bench on June 11, 2008. They work in the building at 100 Court and watched the water come up. They came out to see the water as it began to rise and to have a little fun. Court Ave flooded for a while over the lunch hour after sewers backed up in the intersection of Court and 1st. City of Des Moines brought in two pumps and pumped out the water into the river and the water went away.
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Principal Park, almost completely surrounded by flood water from the Raccoon River, made for a placid backdrop for a bicyclist June 13, 2008. The Iowa Cubs were to host a game Friday night, but the floods forced a cancellation.
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Aerial photo shows how Cedar River flooded over Bremer Avenue, or Iowa highway 3, which runs through Waverly. The flooding on June 10, 2008 extended about eight blocks from the river to within a block of Wartburg College, where the Red Cross has established a shelter. The Bremer Avenue bridge reopened on Wednesday, but the city warned residents that more rain could lead to additional problems.
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Cindy Owsley of La Harpe, Ill., photographs the flooding over County Road 99 in Oakville after volunteering on her fourth day in a row to help fight the flood June 14, 2008. "It hasn't even reached the crest. It's like where's all this water gonna go?" she said.
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Many Iowa City residents were out looking at the floodwater around town June 14, 2008. This is looking north at Highway 6. Iowa City residents were keeping a watchful eye on the water as it nears its crest.
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Looking west across the Burlington bridge shows higher water levels June 15, 2008 at the University of Iowa in Iowa City. Water was pumped into the road from the sewer tunnels to lower the rising level in the tunnel.
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Members of the U.S. Coast Guard head to shore as rain clouds roll in June 14, 2008. They were pulled off the water as the storm came closer. The Coast Guard was there to watch the flooded areas and keep people out of the water.
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Mike Wildman, serviceman for Mid-American, walks the Rocky Shore Drive area trying to shut off the gas at homes that are starting to take on water from the Iowa River June 14, 2008. Iowa City residents were keeping a watchful eye on the water as it nears it's crest.
Register File Photo

Nolan Frey, 6, was helping save his mother's law firm as he fills a canoe with sandbags June 14, 2008. Iowa City residents were keeping a watchful eye on the water as it nears it's crest.
Register File Photo

Kirsten Frey pulls a sandbag-filled canoe out as Ryan Kennedy (left) and Scott Knight (center) bring one back to be loaded June 14, 2008. Iowa City residents were keeping a watchful eye on the water as it nears its crest. They filled a canoe with sandbags and walked them out the building to fortify their sandbag walls.
Register File Photo

Regan and Aurelia Mena of Austin, Texas, and University of Iowa graduates, were originally planning to get married at the Terrace of the Iowa Memorial Union and have the reception at Kinnick Stadium. Flooding on campus forced them to change their wedding to the Englert Theater in downtown Iowa City. They walked to the water and had their photo taken with floaties. They were on their way back to start their party.
Register File Photo

Removing items from the home of John Chase, nearest camera, who lives along Taft Speedway June 10, 2008, in Iowa City. Helping are Jim Carroll, back of boat, Ken Carroll, front left of boat and Pat Heiken, wearing brimmed hat.
Rodney White/The Register

Whitney Teed and Erik Rodgers borrowed a row boat to retrieve some of their belongings from their mobile home June 12, 2008, at the Pleasant Valley Mobile Home Park. Mandatory evacuation was ordered by 6:30p.m. Water from Four Mile Creek and the Des Moines River flooding half the park currently.
Rodney White/The Register

Ron and Laurie Johnson return to their Cedar Rapids neighborhood to retrieve a few clothes on June 12, 2008, after evacuating Wednesday from their city being flooded from the Cedar River breaking levees and cresting over flood stage.
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Iowa City firefighters Darrall Brick and Tina McDermott pull Paul Measells to safety after the truck he was riding in got stuck in the water as he was trying to evacuate June 11, 2008.
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A pig who somehow floated or swam several miles from the flooded hog barns near Oakville, Iowa, attempts to crawl over the levee from the Mississippi River side of a sandbagged levee near Kingston, Iowa, June 17, 2008.
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U. S. Coast Guard petty officers David Rowan, of Keokuk, left and Kevin Saak, of St. Louis, maneuver a boat through Cedar Rapids, Iowa on June 13, 2008, as they help rescue pets in homes surrounded by flood waters. Many pet owners were forced to evacuate quickly earlier in the week, leaving animals behind.
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Billy Ackerson and his wife, Tia, retrieve items on June 9, 2008, in New Hartford from their van, caught in a flood on Sunday. Water reached the steering wheel before receding. Residents of the Butler County town, evacuated as water raced through the streets on Sunday, were allowed back at noon Monday.
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CNN General Assignment Correspondent Sean Callebs stands in the flooded Des Moines River over Saylor Rd and waits to do a live shot June 11, 2008. Callebs is based in New Orleans and covered Hurricane Katrina.
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Pastor Jeff Holub climbs into a sinkhole outside of Fellowship Baptist Church on SE 6th Street while fencing it off June 13, 2008. The sinkhole opened up on Monday and has grown a few feet everyday. He says it was caused by heavy water flow in a nearby storm drain.
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The Register Aerial showing flood damage along the Iowa River flooding Oakville, Iowa, when a levy broke June 16, 2008 just west of town. Photo of farms just on the outskirts of Oakville.
Rodney White/The Register

TOP: Bob Calvert, left, and his wife, Dottie, right, and niece, Reagan Calvert, center, survey the flooding from the Iowa River near Oakville, Iowa June 18, 2008. BOTTOM: Tuesday May 28, 2013 south of Oakville, Iowa. Barn on left and silos at center are the only original buildings from after the flood of 2008.
Rodney White/The Register

TOP: A stranded pig rests on top of a barn June 18, 2008, after floodwaters from the Iowa River broke a levee near Oakville. BOTTOM: The silo and foundations are all that remain 5-years later at this farm south of Oakville on May 28, 2013.
Rodney White/The Register

TOP: A street sign on the corner of 2nd and Willow on the southside of Oakville leans to the east and is littered with corn stalks on July 9, 2008. The streets and yards were covered with dirt and mud. BOTTOM: Corner of Willow and 2nd Streets in Oakville, Iowa on June 5, 2013, a town hit hard by 2008 flooding.
Rodney White/The Register

TOP: Melody Crow puts on her boots to go back to work cleaning up her Oakville home June 9, 2008 so she can one day move back in. The whole first floor of her home has to be gutted because of the mold. She wants to stay in Oakville. BOTTOM: Melody Crow sits in her yard with her "Headless Harry" doll in Oakville June 5, 2013, a town hit hard by 2008 flooding.
Rodney White/The Register

'I don’t think we’re naive' about projected development

Development in the Des Moines area has a big impact on flooding, said Ollendike, Clive's community development director.

"The amount of rainfall in developed spaces has had a continual impact on us," he said, adding that Clive is about a tenth of the 83-square-mile Walnut Creek watershed. But it gets 92 percent of the runoff.

About 400 acres of farmland each year are turned into housing, warehouses and strip malls within the Walnut Creek watershed.

"I don’t think we’re naive (enough) to think we’re going to stop development," Ollendike said. "It’s important for communities. It’s important for Clive. But we need to find that balance, that partnership, where development" has minimal downstream effects.

By 2045, farmland will shrink from about half of the watershed area to a quarter, projections show.

That's why Clive officials have asked the corps and Federal Emergency Management Agency to analyze whether one or a series of lakes, ponds or wetlands could be built upstream to help cut the anticipated increase in urban flooding.

Clive officials also want to know what the threat is before considering whether it should buy out flood-prone homes or require home- and business-owners to raise their properties.

"It's traumatic enough. We don't want to go through it more than once," Ollendike said.

In addition to spending millions of dollars to raise Des Moines' levees, Gano points to the new culvert at 30th Street and Jefferson Avenue as an example of climate change's impact on the city.

Des Moines had to install a pipe 4-feet wider than initially planned "to accommodate the larger flows of rainwater that will come from more frequent and intense rainfalls," the public works director said.

It's part of $110 million the city is investing to replace its decades-old storm sewer pipes, which are to blame for a large amount of damage that hit Beaverdale and other northwest Des Moines neighborhoods.

Unable to make its way into too-small pipes, rainwater flowed between homes, inundating basements that were often unable to withstand the pressure, collapsing walls.

Des Moines leaders are expected to consider raising residents' storm sewer rates over five years to cut in half the time it will take to update the aging sewer system.

"It’s very hard to stand there and say, 'Help is on the way in 10 years,'" Gano said.

'We can't solve our problems with rain barrels'

It may seem over-simplistic, but rain barrels, bioswales and rain gardens could help reduce flooding's devastation within the city, said Josh Mandelbaum, a Des Moines council member.

"We can't solve our problems with rain barrels. But they can be a part of the solution, especially if you target hot-spots, where you know there are backups or where water flows through," Mandelbaum said.